Improved Oxygen Barrier Properties of Poly(Lactic Acid)/Poly(Butylene Adipate-Co-Terephthalate) Composite Films by Combining “Active” and “Passive” Barrier Techniques

To be effectively utilized as packaging materials, the barrier properties of PLA/PBAT composite films must be enhanced. Traditional methods, like the addition of fillers or blending with other polymers usually lead to agglomeration and/or interfacial issues, which are unfavorable for the barrier properties or mechanical performance. In this study, a three-layer co-extrusion blown PLA/PBAT composite film was prepared. Talc was incorporated into the inner and outer layers of the composite film to improve “passive” barrier performance, effectively extending the gas permeation path. In addition, an oxygen scavenger was introduced into the middle layer to react with oxygen that permeates through the composite film, thereby endowing the composite film with “active” oxygen scavenging functionality. The oxygen permeability coefficient of the composite film was decreased significantly from 377 cc·mil·m⁻²·day⁻¹·0.1 MPa⁻¹ of PLA/PBAT film to 26.6 cc·mil·m⁻²·day⁻¹·0.1 MPa⁻¹ of PLA/PBAT composite film, showing a remarkable enhancement of 14.71 times. Moreover, the PLA/PBAT composite film maintained excellent mechanical properties; the longitudinal and transverse tensile strength are 39.4 and 38.9 MPa, respectively; the longitudinal and transverse elongation at break are 508.4% and 543.2%, respectively. This advancement enables the composite film to better meet the stringent requirements of high-performance packaging applications and provides a viable strategy for the development of high-barrier PLA/PBAT composite films.